NEW YORK (CNN) --More than two years after the World Trade Center fell in terrorist attacks, New York has reduced its official death toll from September 11, 2001, by 40 people.

The change from 2,792 to 2,752 is the result of an ongoing review process -- in particular of those initially reported as missing for whom no human remains have been identified.

The city has reduced the September 11 death toll before, but the figure of 2,792 had held steady for more than a year.

"Some of them are alive," said Ellen Borakove, spokeswoman for the city's medical examiner's office, which has been working with the police department and mayor's office on the tally.

In addition to the removal of 40 names, three names are under investigation, Borakove said.

City officials said some of the 40 names removed are thought to be fraudulent claims.

Pinning down an accurate death toll is a problem, primarily because human remains have been recovered for only half of the people believed to have been killed when the hijacked airliners crashed into the 110-story twin towers and the buildings subsequently collapsed.

Officials have positively identified 1,527 victims.

The medical examiner is seeking to identify 1,225 people thought to be killed through DNA testing of thousands of unidentified remains.

"They've been reviewing cases and trying to get information," Borakove said. "There were some people reported missing for whom there was no information -- not even a birth certificate."

At the Ground Zero ceremony commemorating the first anniversary of the attacks, 2,801 names were read and posted on panels attached to a steel viewing fence running along the eastern edge of 16-acre site.

Afterward, nine names -- determined to be duplicates or names of people still alive -- were removed.

Fraud prosecutions in attacks

The Manhattan district attorney and state attorney general have prosecuted two dozen people for filing false claims to collect some of the unprecedented relief funds offered to families of attack victims.

In a trial this year, a jury convicted Cyril Kendall of falsely claiming that his 13th child went to a job interview in the trade center and was killed in the attack.

Kendall received $190,000 from the Red Cross and Safe Horizon, but investigators later found no such child existed.

The city could not immediately provide a breakdown by nationality or reported hometown of the 40 newly removed names.

City officials previously have said roughly half the names reported as missing were believed to be foreign nationals or holders of dual citizenship in a foreign country and the United States.

An estimated 500 foreign nationals from 91 nations were believed to have been killed in the trade center attack.

New York state was home to two-thirds of the trade center victims, and 24 other states lost residents.

The city's original estimate of victims exceeded 6,700, due in part to the large volume of mistaken missing persons reports.

The revised death toll of 2,752 does not include the 10 hijackers who crashed jetliners from American Airlines and United Airlines into the towers.

The number does include the 127 other passengers and 20 crew members on the two flights.